Due to rising environmental restraints placed on the entire chemical industry, there has long been a need to develop more environmentally friendly processes involving less solvent. The automotive industry therefore has been moving more towards the use of waterborne systems for their paint applications. Thus, the goal of many high performance pigment manufacturers is to provide waterborne paints with attributes comparable to their solventborne counterparts.
Chlorinated copper phthalocyanine pigments have been a considerable problem in this area as their attributes in waterborne systems have always been less desirable than their solventborne equivalents. U.S. Pat. No. 5,725,649 discloses chlorinated copper phthalocyanine containing 0-4 chlorine atoms having a crystal size in the range of from 0.01 to 0.2 μm and an ionic complex formed from copper phthalocyanine sulphonic acid and a quaternary amine. This product is produced by either acid pasting or salt ball milling followed by a solvent treatment and exhibits a green down flop in metallic paints. U.S. Pat. No. 5,728,204 discloses a water-dispersible phthalocyanine pigment in combination with a sulfonated copper phthalocyanine, having a mean particle size of about 0.2 to about 0.3 μm and exhibiting a neutral metallic down flop. In this case, the copper phthalocyanine pigment is processed by ball milling without salt followed by optional solvent treatment.
It is noteworthy that both of these prior patents require the use of copper phthalocyanine derivatives, such as sulfonated, anionic phthalocyanine complexes, to obtain the desired effect. Such copper phthalocyanine derivatives have been implicated in paint film problems, such as poor humidity resistance and occurrences of delamination.
Thus, a waterborne system for automotive painting applications without requiring the presence of such ionic additives is desired, in particular, for a waterborne blue exhibiting shade, strength and metallic down travel similar to the current solventborne products.